In order to avoid the addition of excess water or too little water to dry materials, in a concrete truck or the like, to thereby avoid dilution or excess dry material in the mixture, is desirable to provide means for metering the water that is added to the mixture.
In the past, various systems and methods have been proposed in order to provide some degree of control over the water content of the mixture. For example, in U.S. Pat. Nos. 3,593,966 and 4,544,275 a metering system for a concrete mixer is disclosed wherein the inflow of water to the concrete is controlled as a function of the mechanical load on the mixing apparatus, until the load reaches an operator preset value.
U.S. Pat. No. 3,114,478 discloses a metering system for a concrete mixer wherein a water tank mounted on the mixer has an operator settable water quantity dispenser control that permits a determinable amount of water to the dispensed to the mixer.
U.S. Pat. No. 3,631,337 discloses a system for controlling the water added to an aggregate as a function of the moisture entrained in the aggregate.
U.S. Pat. No. 4,654,802 discloses a method for controlling the addition of water to cement, wherein the water is added as a function of the density of the mixed cement.
While such systems enable a determination of the amount of water that was added, or that was to be added, at a given time, they do not ensure that the mixture that was delivered to a job site was not diluted. For example, with such systems, especially those under operator control, the addition of excess water was possible, without a record being maintained of the actual quantity of water added to the mixture. Accordingly, in the past it has been difficult for a concrete supplier to ensure that the concrete that was actually supplied to a job site was of the proper water content. The consequent inability to accurately monitor the addition of water can result in liability of the supplier if a contractor or other user has reason to suspect that the concrete that was supplied was diluted.
Recently, the State of New Jersey has decided that concrete trucks should provide means for monitoring or measuring the amount of water that is added to concrete in concrete trucks, in order to ensure that the concrete is not diluted. At the present time, however, I am not aware of any system that will satisfactorily comply with this requirement.